Unit11 Surface chemistry qns

Unit11 Surface chemistry qns - 1 UNIT 11 SURFACE CHEMISTRY...

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1 QUEST TUTORIALS Head Office : E-16/289, Sector-8, Rohini, New Delhi, Ph. 65395439 UNIT 11 SURFACE CHEMISTRY 1. The enrichment of chemical substances at the surface of a solid is called (a) adsorption (b) absorption (c) isotherm 2. The Gibbs adsorption equation (a) gives the effect of concentration of a solute on the surface tension of solution (b) shows that solutes like soap which lower the surface tension concentrate in the surface (c) shows that solutes like KCl which raise the surface tension concentrate in the bulk of solution (d) all of the above 3. Which of the following characteristics about adsorption is wrong ? (a) adsorption on solids is reversible in nature (b) adsorption, in general, increases with increase in temperarture (c) adsorption is generally selective in nature (d) both enthalpy and entropy of adsorption are negative 4. Freundlich adsorption isotherm decribes the adsorption of gases by solids. The amount of gas adsorbed per gram of adsorbent m x and the pressure (b) of the gas is represented as (a) m x = k p 1/n (b) m x = n / 1 p k (c) p = k n / 1 m x (d) m x = n / 1 p k 5. 100 ml of 0.3 M acetic acid is shaken with 0.8 g of activated charcoal. The final concentration of solution after adsorption is 0.125 M. The weight of acetic acid adsorbed per gram of carbon is (a) 0.125 g (b) 0.0175 g (c) 1.05 g (d) 1.31 g 6. For the adsorption oa a dye from aqueous solution by charcoal at 25ºC, the Freundlich constants are n =3.0, k=0.50 for m x in grams per gram and c in grams per litre. What weight of dye will be adsorbed by 2 grams of charcoal from a litre of solution containing 2 grams of charcol from a litre of solution containing 2 grams of the dye ? (a) 1 g (b) 1.5 g (c) 0.5 g (d) 0.25 g 7. The Langmuir adsorption isotherm is based on the assumption of (a) a constant heat of adsorption (b) a flat solid surface (c) ideal gas behaviour (d) zero activation elergy for adsorption 8. Langmuir adsorption isotherm equation was derived on the basis of (a) uni-molecular layer (b) multi-molecular layers (c) marco-molecular layers (d) all type of layers 9. which of the following gases is likely to be adsorbed by 1 gram of charcoal at s.t.p. ? (a) SO 2 (b) H 2 S (c) H 2 (d) He 10. The molar heat of adsorption of a gas by an adsorbent is 20 kg per mole. It is correct to conclude that (a) it is a case of physical adsorption (b) the gas is adsorbed by Van der Waal’s forces (c) the gas is easily liquifiable (d) all of these 11. The volume of N 2 gas (area per molecule is 16.2 Aº) adsorbed per gram of a finely powdered at s.t.p. is 3.01 c.c. The surface area occupied by the gas in Cm –2 is ( 1Aº = 10 –16 sq.cm.) (a) 1.31 × 10 5 (b) 2.62 × 10 5 (c) 1.31 × 10 6 (d) 2.62 × 10 –16 12. Adsorption explains all the following except (a) origin of charge on colloids (b) decolourization of sugar solution
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2 QUEST TUTORIALS Head Office : E-16/289, Sector-8, Rohini, New Delhi, Ph. 65395439
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This note was uploaded on 10/05/2011 for the course CHEM 1201 taught by Professor Darcy during the Spring '11 term at St. Mary NE.

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Unit11 Surface chemistry qns - 1 UNIT 11 SURFACE CHEMISTRY...

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